This invention relates to a liquid crystal antidazzle mirror used for a vehicle.
A liquid crystal antidazzle mirror which utilizes a liquid crystal is used as one type of an antidazzle mirror in an automobile. This liquid crystal antidazzle mirror alters the light transmission factor of the liquid crystal by controlling a voltage applied to the liquid crystal disposed in front of a mirror to control the reflectivity of the mirror, thereby performing the antidazzle action.
This liquid crystal antidazzle mirror described above necessitates a power source for controlling the light transmission of the liquid crystal. An automotive battery is generally used as this power source for the antidazzle mirror, but it is desirable to supply electric power from the battery when the antidazzle mirror used so as to protect the battery against its discharge since the capacity of the battery is limited. The inventor of this invention has proposed a prior liquid crystal antidazzle mirror which has solved the problem of a decrease in the capacity of the automotive battery as disclosed in Japanese Utility Model Application No. 169708/84. This liquid crystal antidazzle mirror is constructed, as shown in FIG. 3, of a liquid crystal drive control circuit 32 for controlling a voltage applied to a liquid crystal 31, and a key position detecting switch 34 connected between the control circuit 32 and a battery 33 for closing a contact by detecting the fact that a key plate is plugged in a key cylinder when the key plate is inserted into the cylinder to supply power from the battery to the control circuit 32 only when the key plate is plugged in the key cylinder. This antidazzle mirror does not supply power from the battery to the mirror when the key plate is revolved such as to a park position, thereby eliminating problems of a decrease in the charge of the battery or corrosion.
The abovementioned prior liquid crystal antidazzle mirror is effective in energy saving since supplying power from the battery only when the key plate is plugged in a key cylinder. However, when power is supplied from the battery to the antidazzle mirror, it is not apparent whether the antidazzle mirror is disposed in antidazzle or dazzle state and necessary to confirm whether the mirror is disposed in the antidazzle or dazzle state by switching its mode by operating a mode change switch when confirming the rear visual field through the antidazzle mirror immediately after the power is supplied from the battery to the antidazzle mirror, thereby being insufficient at the point of operability.